搜索问题

下面是搜索代码，当我不输入搜索内容时不显示任何内容，我代码的意愿是不输入时显示所有记录

protected void Button1_Click(object sender, EventArgs e)
    {
        string search = "";
        if (this.Suserid.Text != "")
        {
            search = "userid=" + Convert.ToInt32(this.Suserid.Text) + "";
            if (Susername.Text != null)
            {
                search += "and username ='" + Susername.Text + "'";
            }
            else
            {
                search += "and username like '%'";
            }


        }
        else
        {
            search = "userid <>null ";
            if (Susername.Text != null)
            {
                search += "and username ='" + Susername.Text + "'";
            }
            else
            {
                search += "and username like '%'";
            }
        }
      

              


        DataView dv = new DataView(opends("user").Tables["user"]);
        dv.RowFilter = search;
        DataGrid1.DataSource = dv;
        DataGrid1.DataBind();
    }